The present invention relates to selected 2-aryl-2H-benzotriazoles which are useful in protecting light-sensitive organic materials from deterioration and to stabilized compositions containing said benzotriazoles.
The UV-absorber of the o-hydroxyphenyl-2H-benzotriazole class have long been known as effective light stabilizers for organic materials and have enjoyed considerable commercial success.
The description, preparation and uses of these valuable 2-aryl-2H-benzotriazoles are further taught in U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615 and 3,230,194.
However the hitherto known 2-aryl-2H-benzotriazoles of this group have in some circumstances exhibited limited compatibility in certain substrates, and excessive tendency to exude, sublime and/or volatilize during processing of stabilized compositions into sheets, films, fibers or other pellicles when processing must be done at elevated temperatures. Likewise such benzotriazoles may also suffer undue loss by volatilization or sublimation from fabricated structures, particularly thin films or coatings, especially when subjected to elevated temperatures during use.
Attempts have been made to increase compatibility and to reduce volatilization loss by modifying the structure of the benzotriazoles.
In U.S. Pat. No. 3,230,194, a higher alkyl group was substituted for methyl and the compound 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole exhibited superior compatibility and performance in polyethylene.
In U.S. Pat. No. 4,127,586, still other modifications to the 2-aryl-2H-benzotriazole moiety were made to increase still further compatibility in substrates and resistance to volatilization. The compound 2-[2-hydroxy-3-(1-phenylethyl)-5-methylphenyl]-2H-benzotriazole described therein exhibited better compatibility and better resistance to loss by volatilization during processing than did the earlier prior art benzotriazole compounds.
In Japanese Kokai 158588/75, other benzotriazole light stabilizers such as 2-(2-hydroxy-3-.alpha.,.alpha.-dimethylbenzyl-5-methylphenyl)-2H-benzotria zole are disclosed.
However, still better resistance to loss from stabilized compositions during high temperature processing remained a practical objective and need in the art for the benzotriazole UV-absorbers.
The instant compounds such as 2-[2-hydroxy-3,5-di-(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazo le exhibit surprisingly superior resistance to loss from stabilized compositions during high temperature processing or in end use applications where coatings or films of the stabilized compositions are exposed even to ambient weathering and light exposures compared to stabilized compositions containing the 2-aryl-2H-benzotriazoles of the prior art.
In U.S. Pat. No. 4,041,044 an improved process for making 2-aryl-2H-benzotriazoles is taught. In the broadest generic scope in said reference, 2-[2-hydroxy-3,5-di-(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-benzotriazo le and 5-chloro-2-[2-hydroxy-3,5-di-(.alpha.,.alpha.-dimethylbenzyl)phenyl]-2H-be nzotriazole are disclosed. Neither compound was exemplified nor prepared in said reference and the outstanding properties of these compounds now seen compared to other prior art benzotriazoles were not then recognized from the myriad of possible compounds generically disclosed in this reference.